How to Tell If Your Furnace Ignitor Is Bad

The quickest way to tell if a furnace ignitor is bad is to watch and listen to what happens at start-up. A healthy ignitor glows bright orange within a minute of the thermostat calling for heat, and the gas lights a few seconds later. If that glow never shows up, the ignitor is the first part to suspect. This guide covers the signs, the checks you can safely do yourself, and the point where it becomes a technician’s job.

How to Tell If a Furnace Ignitor Is Bad: The Short Answer

Turn the thermostat up a few degrees and watch one full start-up. First the small inducer fan starts, then the ignitor should glow, and then the gas valve opens and the burners light. If the inducer runs but there is no glow at all, suspect the ignitor first, though a pressure switch that never closes looks the same. When it glows faintly or in patches, or shows a crack or a white spot, it is on its way out, while a bright glow with no gas following points to the valve or board. A multimeter test can confirm it, which we explain below.

What a Normal Start-Up Looks Like

When the thermostat calls for heat, the control board starts the inducer motor, which clears the combustion area and proves the vent is open through a pressure switch. Only then does the board send power, 120 volts on most models, to the ignitor, which heats for somewhere between 15 and 45 seconds depending on the brand. Once it is hot enough to ignite the gas, the valve opens and a sensor has a few seconds to confirm there is a flame. The main blower usually follows about half a minute later, once the heat exchanger has warmed up. Because each step waits on the one before it, the place where the sequence stops tells you a lot. Our guide to how a gas furnace operates walks through the full cycle if you want more detail.

Signs of a Bad Furnace Ignitor

Most ignitors give a homeowner some warning before they quit completely, although in a Calgary cold snap the warning period can be short.

No Glow and No Heat

The clearest sign is an inducer that runs with no glow following it. Some furnaces let you see it through a small window or slots in the burner door, while on others the door switch, a safety feature, cuts the electricity when the panel comes off, and it should never be taped or held down. If the ignitor stays dark while everything before it runs, either the element is broken or the board is not sending it any current, and a meter test separates the two.

Cold Air From the Vents

If the thermostat is set to heat and the vents are blowing cool air, the gas is not lighting or not staying lit, and a faulty ignitor is one common reason. The blower may be set to run continuously, or it may be finishing its cool-down run after the flame dropped out, so air moves but carries no heat. Check that the thermostat is on heat and the fan setting is on auto before you blame any part of the heating system.

Repeated Clicking and Restart Attempts

A hot surface ignitor makes no noise of its own, so the clicks you hear are relays on the control board and the gas valve. When the furnace clicks, pauses, runs the inducer again and repeats that several times, it is retrying an ignition that keeps failing. Most boards give up after three or four tries and go into lockout, usually for about an hour, before trying again.

Short Cycling

A weak ignitor sometimes manages to ignite the gas only on the second or third try, so the furnace seems to turn on and off more than it should. That said, the problem has plenty of other causes, including an overheating furnace, a dirty flame sensor and a badly placed thermostat. Our page on what causes a furnace to short cycle covers those, and it is worth ruling them out before replacing parts.

Cracks, White Spots or Discolouration

A good silicon carbide ignitor is an even grey, while silicon nitride versions are usually dark and rounded. Hairline cracks, white or pale patches, and any section that looks blistered are signs of physical damage. An element in that state can still glow for a while, but it rarely lasts, and it tends to fail when the furnace is working hardest.

A Tripping Breaker

A shorted ignitor or a pinched wire near it can trip the furnace circuit breaker. However, a breaker that trips repeatedly can also point to a motor or another electrical fault, so this sign alone does not confirm the ignitor. Leave the breaker off and call a professional.

Is It the Ignitor or Something Else?

Plenty of parts in the system produce the same “no heat” problem, and replacing the ignitor on a guess is a common way to spend money without fixing anything. If the burners light and then go out after three to ten seconds, the ignitor has done its job and the flame sensor is not proving the flame. That is usually a dirty sensor rod, and our guide to cleaning a flame sensor on a furnace shows how to deal with it. If the inducer runs but the ignitor never gets its turn, the pressure switch may not be closing, and that check is best left to a technician. When the inducer never starts at all, the issue sits earlier in the chain.

The control board is the other common culprit. An ignitor that tests fine on a meter but never glows is often waiting on a board that is not sending it voltage. Most furnaces also have a status light that blinks a fault code, and the chart printed inside the furnace door usually explains what the flashes mean. Before any of that, rule out the simple things: the furnace switch, the gas supply valve, a clogged filter and a thermostat that needs batteries.

How to Check a Furnace Ignitor Yourself

A basic check needs only a flashlight, a screwdriver and a multimeter, as long as you treat the element gently. Switch the furnace off at its service switch, close the gas valve if you plan to handle anything, and give the burner area several minutes to cool. Next, remove the upper panel and find the ignitor, which sits at the end of the burner row on a small bracket with two wires leading to a plug.

Look before you touch. Shine the flashlight on the element and check for cracks, white spots and dark blisters, along with a loose connector or a burnt wire. Never touch the element itself with your fingers, since skin oil leaves a hot spot that can crack it, and even light pressure can snap it. If the ignitor is only dusty, the right way to clean it is a puff of air and nothing abrasive.

Testing a Hot Surface Ignitor With a Multimeter

Unplug the ignitor at its connector, pulling on the plug rather than the wires. Set the meter to the lowest ohms range and touch one probe to each pin on the ignitor side. Most silicon carbide ignitors read roughly 40 to 90 ohms at room temperature, while silicon nitride models read lower, often around 10 to 20 ohms. The part label or the furnace manual gives the exact range for yours.

An open reading, shown as OL or infinite, means the element is broken inside and needs replacing. A reading well above the normal range usually means it is worn, so it may still glow but not hot enough to light the gas reliably. When the reading sits inside the range and the ignitor still does not glow, the element is likely fine and the issue is upstream. Checking for voltage at the plug during a start-up means working on live 120 volt wiring, so that part is best left to a technician.

How Can You Test the Spark Ignitor in Your Furnace?

Some furnaces use a spark ignitor instead of a glowing element, either lighting the main burners directly or lighting a small intermittent pilot first. At start-up, you should hear a steady ticking and, through the viewing window, see a bright blue spark jumping from the electrode tip to the burner or pilot hood. No ticking, a weak orange spark, or a spark that jumps somewhere else all point to a problem.

With the furnace off, check for a cracked white porcelain insulator, a worn or dirty tip, a loose high voltage lead and the wrong spark gap. The gap is usually about 3 mm, roughly an eighth of an inch, but your furnace manual has the real number. Never hold the lead or electrode while the furnace is trying to start, because the spark runs at thousands of volts. If the spark looks healthy and the pilot light still will not catch, the likely issue is gas supply or a blocked pilot orifice, and that is work for a certified gas fitter.

What Is the Life Expectancy of a Furnace Ignitor?

Most hot surface ignitors last roughly four to seven years, and the tougher silicon nitride type often outlasts the older silicon carbide design. Calendar age matters less than the number of starts, because every heating cycle takes the element from room temperature to above 1,000 degrees Celsius and back again. A Calgary heating season can run from September into May, so furnaces in our homes rack up far more starts than in a milder climate.

Several things shorten that life beyond normal wear and tear. A furnace that turns on too often burns through its starts faster, and a clogged filter makes the whole cabinet run hotter. Changing the filter on schedule helps, and our guide on how often you should change the filter in your furnace gives the timing. Power surges, loose electrical connections and fingerprints left on a new element during installation are the other usual causes of early failure, and a regular tune-up can prevent the loose-connection kind.

What Is the Average Cost to Replace a Furnace Ignitor?

At Calgary Air Heating and Cooling Ltd, an ignitor replacement typically falls between $250 and $450, depending on the furnace and the part it takes. Our diagnostic service call is $149, or $289 for evenings and weekends during heating season. We keep pricing transparent, with no hidden fees, and our guide to what furnace repairs cost in Calgary lists the other common parts alongside the ignitor.

Replacing the ignitor is one of the more affordable furnace repairs, and on a system in good shape it is almost always worth doing. Some guides treat the swap as a DIY job, but the part is fragile, has to match your model, and a wrong one can damage the control board, so test before you buy. The exception is an older heating system with other problems stacking up. If the ignitor is the third part to fail this winter on a furnace near the end of its life, it may be time to look at our furnace replacement service and get a free quote before spending more on repairs. Our guide on how to tell how old your furnace is helps if you are not sure where yours stands, and our furnace installation service covers the Lennox, Tempstar, Goodman and Trane units we put in. When you just want the heat back, our furnace repair team handles ignitors on all major brands, whoever installed the equipment.

Can You Reset a Furnace Ignitor?

There is no reset on the ignitor itself. What you can reset is the furnace, which clears a lockout after several failed ignition attempts, and our article on how to reset your furnace shows how to do that safely. If the furnace locks out again within a day or two, a reset is only hiding the fault, and the ignitor or sensor needs a proper look.

When to Stop and Call a Technician

Some signs mean you should stop troubleshooting altogether. Gas smell is a different issue entirely: if you notice one, leave the home and call ATCO’s emergency line at 1-800-511-3447 from outside. A loud bang or whoomp at start-up is delayed ignition, which means gas builds up before it catches, so switch the furnace off and have it checked. The same applies to scorch marks near the burners, a tripping breaker, or any time you are unsure how to shut off the gas or electricity.

A yearly visit through our furnace maintenance service is a good time to have the ignitor and flame sensor looked at, and a weak element found in October is far easier to deal with than a no heat call in January. If your furnace is showing any of these signs, call Calgary Air Heating and Cooling Ltd at (403) 720-0003. We serve Calgary, Chestermere, Cochrane and Okotoks, with evening and weekend appointments available.